You can generally combat over hydration with just gradually adding in more flour....however....enriched cakes generally have a lot more ingredients in them and those should to be in balance too. I would normally just say double the rest of the ingredients (hydrating the yeast with just enough water to make it into a paste) and make more cake. You mentioned that you don't have enough ingredients though, for another batch, so that may not be an option. You can still try to add as much as you have, but you will end up with a different product. With most breads, as long as the liquid, flour, yeast and salt are in balance, you can get away with altering the rest of the ingredients (sugar, fat, flavors) without too much ill effect.